Time-delay relay and method of assembling same

ABSTRACT

A time-delay relay comprising a housing having a chamber in which are mounted a thermostatic switch assembly and an electric heater in heat transfer relation with the thermostatic switch assembly for heating the latter to effect actuation of the contacts thereof. A pair of heater terminals are positioned in terminal-receiving slots in the housing, and have portions in conductive electrical contact with the heater. A cover overlies the thermostatic switch assembly and has means engageable with the terminals thereby to retain the terminals within the housing. A retainer is provided which is snapped into a position spanning the mouth of the chamber thereby to hold the terminals, heater, thermostatic switch assembly, and the cover in their assembled position. Also disclosed is a method of assembling a time-delay relay in which the various components are inserted into respective openings in a chamber of a housing and in which the various components are secured relative to one another and relative to the housing by means of a retainer.

United States Patent [1 1 Hancock TIME-DELAY RELAY AND METHOD OFASSEMBLING SAME [75] Inventor: John T. Hancock, Garland, Tex.

[73] Assignee: Texas Instruments Incorporated,

Dallas, Tex.

[22] Filed: July 30, 1973 [21] Appl. No.: 383,946

Primary Examiner-J. D. Miller Assistant Examiner-Fred E. Bell Attorney,Agent, or Firm-John A. Haug; James P. McAndrews; Edward J. Connors [4 1Dec. 31, 1974 5 7] ABSTRACT A time-delay relay comprising a housinghaving a chamber in which are mounted a thermostatic switch assembly andan electric heater in heat transfer relation with the thermostaticswitch assembly for heating the latter to effect actuation of thecontacts thereof. A pair of heater terminals are positioned interminalreceiving slots in the housing, and have portions in conductiveelectrical contact with the heater. A cover overlies the thermostaticswitch assembly and has means engageable with the terminals thereby toretain the terminals within the housing. A retainer is provided which issnapped into a position spanning the mouth of the chamber thereby tohold the terminals, heater, thermostatic switch assembly, and the coverin their assembled position. Also disclosed is a method of assembling atime-delay relay in which the various components are inserted intorespective openings in a chamber of a housing and in which the variouscomponents are secured relative to one another and relative to thehousing by means of a retainer.

11 Claims, 6 Drawing Figures TIME-DELAY RELAY AND METHOD OF ASSEMBLINGSAME BACKGROUND OF THE INVENTION This invention relates to thermostaticelectrical switches and is particularly concerned with a timedelay relat(TDR) utilizing a thermostatic switch assembly for opening and closingan electrical circuit.

More particularly, this invention is concerned with a TDR in whichcertain electrical terminals and a thermostatic switch assembly are heldin position relative to one another and relative to a housing by meansof a retainer adapted to be snapped into position in a chamber in thehousing. In prior art TDRs the thermostatic switch assembly wasadhesive-bonded or riveted to a housing and electrical terminals wereriveted to the housing. The adhesive bonding procedure required that theadhesive be cured, and this curing cycle increased the assembly time ofthe unit. Both the application of the adhesive and the installation ofthe rivets for the terminals involved separate manufacturing steps whichincreased production time and costs. Known prior art assembly procedureshave required the TDR components to be brought together along differentaxes or planes (e.g., both vertical and horizontal) therebynecessitating that the unit be turned during assembly thus resulting inincreased production time and requiring complicated production machines.

SUMMARY OF THE INVENTION Among the several objects of this invention maybe noted the provision of a TDR which may be assembled without the useof adhesive or rivets; the provision of such a TDR in which all partsmay be brought together along one axis or plane (e.g., a vertical one)thereby to simplify assembly; the provision of such a TDR in whichterminals may readily be installed in the housing without the use ofrivets; the provision of such a TDR which, once assembled, substantiallyprecludes tampering; the provision of such a TDR in which many of thecomponents thereof perform multiple functions; the provision of a methodof assembling a TDR unit which simplifies the assembly procedure of TDRsand which results in increased production at lower cost; and theprovision of such a TDR which is of rugged contruction and is reliablein operation. Other objects and features of this invention will be inpart apparent and in part pointed out hereinafter.

Briefly, a time-delay relay unit of this invention comprises a housinghaving a chamber and terminalreceiving slots therein. A thermallyresponsive switch assembly adapted to make and break an electricalcircuit is mounted within the chamber. This switch assembly has contactsand a thermostatic switch element therewithin, the contacts beingmovable into and out of engagement with one another in response toactuation of the thermostatic element when the latter is subjected topredetermined temperature conditions. A heater energized by a secondcircuit is positioned in a heattransfer relation with the switchassembly for heating the thermostatic element. A pair of terminalsadapted for electrical contact with the heater is provided in thehousing, these terminals constituting a portion of the second circuit.The heater and the switch assembly are mounted within the chamber, andthe terminals are received by the terminal-receiving slots in thehousing. A

cover overlies the chamber and has means engageable with the terminalsthereby to retain the terminals within the housing. A retainerengageable with the housing is forced into position at the mouth of thechamber thereby to hold the cover, the switch assembly, the heater andthe terminals in an assembled relation relative to one another withinthe housing.

The method of this invention of assembling a timedelay relay unitcomprises first inserting the terminal members into the openings in thehousing with portions of the terminals extending into the chamber. Then,the heater and the switch assembly are inserted into the chamber withthe heater in electrical contact with the above-mentioned portions ofthe terminals and in heattransfer relation with the switch assembly. Acover is then installed in the chamber to overlie the switch assemblyand the heater, the cover being engageable with the terminal members,and then a retainer is applied across the mouth of the chamber, theretainer being engageable with the housing at the sides of the chamberthereby to positively secure the terminal members, the heater, theswitch assembly and the cover in an assembled position relative to thehousing.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of atime-delay relay (TDR) of this invention;

FIG. 2 is an enlarged plan view of the TDR;

FIG. 3 is a vertical section taken on line 3-3 of FIG. 2 with partsbroken away to show some interior details;

FIG. 4 is an enlarged partial plan view of a portion of the TDR housingprior to installation of the terminals and switch assembly; and

FIGS. 5 and 6 are front views of the two heater terminals.

Corresponding reference characters indicate corresponding partsthroughout the several views of the drawings.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the drawings, atime-delay relay unit (TDR) of this invention, indicated in its entiretyat l, is shown to comprise a housing 3 of nonconductive material (e.g.,a molded synthetic resin) having a chamber 5 and a pair ofterminal-receiving slots 7a, 7b molded therein. An enclosed unitarythermostatic switch assembly 9 is mounted within chamber 5. This switchassembly includes a case 11 adapted for reception in chamber 5 and apair of contacts 13a, 13b mounted within the case.

As shown in FIG. 3, contact is mounted on a bracket 15 and contact 13bis secured to the free end of a contact arm 17 resiliently cantileveredfrom one side of the switch casing and being movable therewithin tobring contact 13b into and out of mating engagement with contact 130.Contacts 13a, 13b are normally biased closed by the arm 17.

A thermostatic element 19 such as a snap-acting bimetallic disk of thetype disclosed, for example, in US. Pat. No. l,448,240, is mountedwithin case 11. Because of its nondevelopable or dished shape element 19will snap from one curvature position to an opposite one in response tochange of temperature so as to provide mechanical power to actuate thecontact arm l7 of switch assembly 9. Disk 19 is mounted at the bottom ofcase 11 within a cup-shaped end closure 21 thereof which is formed froma material such as copper having good electrical and thermalconductivity. The periphery of disk 19 is supported by an internalshoulder 23 of cup 21. A pill-shaped heater 25 is bonded inheat-transfer relation to the undersurface of cup 21, this heaterconstituting means for heating disk 19. This heater may be formed of amaterial with a resistivity-temperature curve having a steep-slopedpositive temperature coefficient (referred to as PTC) such as isdescribed and illustrated in US. Pat. No. 3,489,976. At temperaturesbelow a predetermined elevated temperature, the bimetallic disk isdish-shaped with its upper face concave (see FIG. 3). Upon being heated,the disk snaps over center so that its upper face is convex. An actuatoror transfer pin 26 is axially slidable within a central bore of acylindrical pin guide 27 so that when disk 19 snaps into its convexupward curvature it will be moved upwardly to engage a lobe 28intermediate the ends of contact arm 17 thereby to lift arm 17 to opencontacts 13a, 13b.

A pair of terminals 29a, 29b is inserted in their respective receivingslots 7a, 7b in housing 3 (one terminal in each slot). Each terminal29a, 29b has a contact portion 31a, 31b, respectively which extends intochamber so that the contact portion 31a of terminal 29a engages andelectrically contacts the central undersurface of heater 25 and contactportion 31b of terminal 29b engages and electrically contacts cup 21,which constitutes the other terminal of heater pill 25. Thus, terminals29a, 29b and heater 25 form a heater circuit to which electrical poweris supplied for heater energization.

Switch assembly 9 includes a pair of terminals 33a, 33b, each connectedto a respective contact 13a, 13b, these terminals and contactsconstituting an electrical circuit which is opened in delayed responseto energization of the heater circuit by disk 19 snapping overcenter andopening contacts 13a, 13b. It is to be understood that the arrangementof the disk and contacts may be such that the contacts will be opened orclosed on a rise in temperature.

Terminals 29a, 29b are substantially identical in structure in theirupper portions, both including a shank portion 35a, 35b, a quick-connectportion 37a, 37b with shoulders 39a, 3% between the shank andquickconnect external terminal portions 37a, 37b and with shoulders 41a,41b at the lower ends of the shank portion. Each terminal has a tab 43a,43b struck from the shank portion with its free upper end extendingoutwardly from the shank portion and inwardly toward chamber 5 when theterminal is received in its respective terminal-receiving slot 7a, 7b.As shown in FIG. 3, contact portion 31a of terminal 29a is an elongatearm extending into chamber 5 for firm electrical contact with theundersurface of heater 25. And contact portion 31b of terminal 33b hasits relatively short contact finger 31b struck from its shank 35b so asto extend into the chamber for electrical contact with the periphery ofcup 21, and thus conductive electrical contact with the top surface ofheater 25. Terminals 29a, 29b are preferably made of a resilientelectrical conductor material, such as a good cooper electrical alloy.The contact portions 31a, 31b are formed so as to be biased intoresilient firm engagement with heater 25 and with cup 21, respectively,thereby to maintain excellent electrical contact therewith.

Terminal-receiving slots 7a, 7b in housing 3 are identical, and thusonly one slot need be described in detail. Each slot includes a thin,blind slot 45 (see FIG. 4) in the housing generally parallel to the axisof chamber 5 for reception of the shank portions 31a, 31b of a respective terminal 29a, 29b inserted therein, and a connecting slot 47extending heightwise of the chamber along the length of the shank slotproviding an opening between the chamber and-the shank slot thusenabling the contact portions 31a, 31b of the terminals to extend fromthe shank-receiving slot into the chamber. Within each shank-receivingslot 45 are stops 49(see FIG. 3) engageable with shoulders 41a, 41b atthe bottom of the shank of each terminal 29a, 29b thereby to properlyposition each terminal in the housing upon being inserted into itsrespective slot 7a, 7b. As indicated at 51, stops are provided inhousing 3 on the walls of chamber 5, these stops being engageable by theperiphery of cup 21 of switch assembly 9 thereby to position the case 11when it is seated in the chamber in an assembled position in whichheater 25 and cup 21 are properly located within the housing forelectrical contact with contact portions 31a, 31b of terminals 29a, 29b.

As best seen in FIGS. 2 and 4, chamber 5 is a blind hole of generallycircular cross section and has a mouth 53 of generally rectangular crosssection. A cover of insulating material, generally indicated at 55, fitswithin the mouth of the chamber, to engage the upper surface of case 11of the unitary thermostatic switch assembly 9 and to hold the latter inits installed seated position in the chamber. Cover 55 is of generallyrectangular shape in plan and has a close fit (but not a tight fit)within the mouth of the chamber. The cover has lugs 57 extending fromopposite ends of the cover into slots 47 which engage the inner faces ofshank portions 35a, 35b and the upper free ends of tabs 43a, 43b ofterminals 29a, 29b, thereby preventing movement of the terminals andretaining them in their installed position in the housing. As indicatedat 59, cover 55 has a plurality of gripping ledges on its undersurfacefor engagement with the upper portion of switch body 11 of switchassembly 9 thereby to hold the latter in its installed position.

A retainer 61, adapted to be forced or snapped into a locking positionin chamber mouth 53, positively holds and locks the cover in position inthe housing. With the cover lugs 57 in engagement with tabs 43a, 43bterminals 29a, 29b and with cover ledges 59 in engagement with switchbody 11 of switch assembly 9, all the components of the time-delay unitare securely held relative to one another and relative to housing 3 inan assembled position by means of retainer 61. MOre particularly,retainer 61 is preferably made of a stiff, resilient material, such asspring steel. The retainer is generally of rectangular shape in plan andhas tabs 63 extending endwise therefrom. Tabs 63 are bent up from theplane of the main section of the retainer and the length of the retainerfrom one tab to another is slightly greater than the interior dimensionsof chamber mouth 53 whereby, upon installation of the retainer, theretainer must be forced into the chamber mouth. With the retainerproperly installed, it is contiguous to the upper surface of cover 55and securely holds the latter in position relative to the housing.Preferably, cover 55 is made of an electrically insulative material,such as a thermosetting synthetic resin, thereby to electricallyinsulate the switch assembly from retainer 61. It will be further notedthat, upon installation of retainer 61 in chamber mouth 53, retainertabs 63 are deformed or sprung so as to have an interference fit orengagement with opposing surfaces of the housing at the mouth of thechamber as the retainer is pushed into the chamber mouth. With tabs 63being bent up away from the main section of the retainer, any attempt toremove an installed retainer from the chamber mouth will cause the endsof the tabs to dig into the side walls of the chamber mouth and thuseffectively prevent removal of this retainer. This self-tightening orself-locking feature of the retainer prevents tampering with thetime-delay relay unit after assembly.

In accordance with this invention, a simpler, more rapid and less costlymethod of assembly is accomplished by first inserting terminal members29a, 29b into their respective terminal-receiving slots 7a, 7b inhousing 3. Case 11 enclosing unitary thermostatic switch assembly 9,along with heater 25 secured to the bottom thereor, is then insertedinto its installed position in chamber 5 with the contact portions 31a,31b of terminals 29a, 29b in electrical contact with the heater and withcup 19 respectively and with the heater in heat transfer station withthe cup. Cover 55 is then placed in chamber mouth 53 with lugs 57extending into contact-receiving slots 47 for engagement with tabs 41 onterminals 29a, 29b and with ledges 59 in engagement with switch body 11.Retainer 61 is then snapped into position in chamber mouth 51 abovecover 55 thereby positively to secure terminals 29a, 29b, switchassembly 9 and cover 55 in their respective assembled positions (seeFIG. 3) relative to housing 3. The method of assembling a time-delayrelay unit of this invention eliminates the need for adhesive bondingthe switch assembly to the housing, permits all parts to be broughttogether during assembly along a common vertical axis or plane,eliminates the need to rivet heater terminals 29 a, 29 b to the housing,and provides an assembled unit which is of small over-all size and whicheffectively eliminates tampering with the unit after assembly.

n view of the above, it will be seen that the several objects of theinvention are achieved and other advantageous results attained.

As various changes could be made inthe above constructions and methodswithout departing from the scope of the invention, it is intended thatall matter contained in the above description or shown in theaccompanying drawings shall be interpreted as illustrative and not in alimiting sense.

What is claimed is:

1. A time-delay relay comprising:

a housing having a chamber and terminal receiving slots therein;

a thermally responsive switch assembly mounted within said chamber andhaving contacts and a thermostatic element, said contacts being movableinto and out of engagement with one another in response to actuation ofthe thermostatic element when the latter is subjected to predeterminedtemperature conditions thereby to make and break a first circuit;

a heater in heat-transfer relation with said switch assembly for heatingsaid thermostatic element, said heater being energized by a secondcircuit;

a pair of terminals adapted for conductive electrical contact with saidheater, said terminals constituting a portion of said second circuit,said heater and said switch assembly being mounted within said chamberand said terminals being received by said terminal receiving slots insaid housing; a cover overlying said chamber and having means engageablewith said terminals thereby to retain the terminals within said housing;and

a retainer engageable with said housing adapted to be forced intoposition at the mouth of the chamber thereby to hold the cover, switchassembly, heater and terminals in assembled relation within saidhousing.

2. A time-delay relay as set forth in claim 1 wherein said chamber is ablind hole in one face of the housing, this one face of the housingconstituting the top of the housing, said terminal-receiving slots beingadjacent said chamber and extending generally parallel to the chamber,each said slot having a portion thereof opening into said chambersubstantially along the length of said slot.

3. A time-delay relay as set forth in claim 2 wherein each terminal hasa shank portion adapted to be received by said slot upon insertion ofits lower end into the slot from above, a contact portion extending fromthe shank portion through said slot portion and into the chamber forconductive electrical contact with said heater.

4. A time-delay relay as set forth in claim 3 wherein each terminal hasa tab struck from its shank portion, said tab angling away from saidshank portion and inwardly and upwardly toward said chamber, said tabbeing received within said portion of said slot and being engageable bysaid means on said cover thereby to retain the terminals within thehousing.

5. A time-delay relay as set forth in claim 4 wherein each said slot hasa stop therewithin engageable by a respective terminal inserted thereinfor positioning the terminal in a desired installed position within theslot relative to the housing in which said contact portion is inposition for conductive electrical contact with said heater.

6. A time-delay relay as set forth in claim 2 wherein said means on saidcover engageable with said terminal comprises a pair of lugs, one foreach terminal, each lug extending into said portion of saidterminal-receiving slot and being engageable with a respective terminal.

7. A time-delay relay as set forth in claim 6 wherein said cover isengageable with said thermally responsive switch assembly thereby tohold the switch in position within said housing.

8. A time-delay relay as set forth in claim 7 in which said thermallyresponsive switch assembly is an enclosed unitary assembly and saidheater is secured to the undersurface thereof.

9. A time-delay relay as set forth in claim 1 wherein said retainer ismade of a relatively stiff, resilient material and is of a lengthsomewhat longer than the distance from one side to the other of themouth of said chamber, portions of said retainer adjacent the sides ofthe chamber being forced into engagement with opposing surfaces of thehousing at the mouth of the chamber, said portions of the retainerpreventing removal of the retainer from the housing once it has beenforced into position.

10. A time-delay relay as set forth in claim 9 wherein the mouth of saidchamber is rectangular in cross section and said retainer is generallyin the shape of a rectangle having a plurality of tabs extending endwisetherfrom, said tabs being bent up from the plane of said retainer andbeing engageable with opposite sides of the mouth of the chamber therebyto lock the retainer relative to the housing upon inserting the retainerinto the mouth of the chamber.

11. A method of assembling a time-delay relay, said relay comprising ahousing with a chamber and with openings for the reception of terminalmembers, a thermostatic switch assembly, a heater for heating saidswitch assembly, and a pair of terminal members for supplying electricalpower to the heater, said method comprising the steps of:

inserting said terminal members into said openings in the housing,portions of said terminals extending into said chamber;

inserting said heater and said switch assembly into said chamber withthe heater in conductive electrical contact with said portions of theterminals and in heat-transfer relation with the switch assembly;

position relative to the housing.

1. A time-delay relay comprising: a housing having a chamber andterminal receiving slots therein; a thermally responsive switch assemblymounted within said chamber and having contacts and a thermostaticelement, said contacts being movable into and out of engagement with oneanother in response to actuation of the thermostatic element when thelatter is subjected to predetermined temperature conditions thereby tomake and break a first circuit; a heater in heat-transfer relation withsaid switch assembly for heating said thermostatic element, said heaterbeing energized by a second circuit; a pair of terminals adapted forconductive electrical contact with said heater, said terminalsconstituting a portion of said second circuit, said heater and saidswitch assembly being mounted within said chamber and said terminalsbeing received by said terminal receiving slots in said housing; a coveroverlying said chamber and having means engageable with said terminalsthereby to retain the terminals within said housing; and a retainerengageable with said housing adapted to be forced into position at themouth of the chamber thereby to hold the cover, switch assembly, heaterand terminals in assembled relation within said housing.
 2. A time-delayrelay as set forth in claim 1 wherein said chamber is a blind hole inone face of the housing, this one face of the housing constituting thetop of the housing, said terminal-receiving slots being adjacent saidchamber and extending generally parallel to the chamber, each said slothaving a portion thereof opening into saiD chamber substantially alongthe length of said slot.
 3. A time-delay relay as set forth in claim 2wherein each terminal has a shank portion adapted to be received by saidslot upon insertion of its lower end into the slot from above, a contactportion extending from the shank portion through said slot portion andinto the chamber for conductive electrical contact with said heater. 4.A time-delay relay as set forth in claim 3 wherein each terminal has atab struck from its shank portion, said tab angling away from said shankportion and inwardly and upwardly toward said chamber, said tab beingreceived within said portion of said slot and being engageable by saidmeans on said cover thereby to retain the terminals within the housing.5. A time-delay relay as set forth in claim 4 wherein each said slot hasa stop therewithin engageable by a respective terminal inserted thereinfor positioning the terminal in a desired installed position within theslot relative to the housing in which said contact portion is inposition for conductive electrical contact with said heater.
 6. Atime-delay relay as set forth in claim 2 wherein said means on saidcover engageable with said terminal comprises a pair of lugs, one foreach terminal, each lug extending into said portion of saidterminal-receiving slot and being engageable with a respective terminal.7. A time-delay relay as set forth in claim 6 wherein said cover isengageable with said thermally responsive switch assembly thereby tohold the switch in position within said housing.
 8. A time-delay relayas set forth in claim 7 in which said thermally responsive switchassembly is an enclosed unitary assembly and said heater is secured tothe undersurface thereof.
 9. A time-delay relay as set forth in claim 1wherein said retainer is made of a relatively stiff, resilient materialand is of a length somewhat longer than the distance from one side tothe other of the mouth of said chamber, portions of said retaineradjacent the sides of the chamber being forced into engagement withopposing surfaces of the housing at the mouth of the chamber, saidportions of the retainer preventing removal of the retainer from thehousing once it has been forced into position.
 10. A time-delay relay asset forth in claim 9 wherein the mouth of said chamber is rectangular incross section and said retainer is generally in the shape of a rectanglehaving a plurality of tabs extending endwise therfrom, said tabs beingbent up from the plane of said retainer and being engageable withopposite sides of the mouth of the chamber thereby to lock the retainerrelative to the housing upon inserting the retainer into the mouth ofthe chamber.
 11. A method of assembling a time-delay relay, said relaycomprising a housing with a chamber and with openings for the receptionof terminal members, a thermostatic switch assembly, a heater forheating said switch assembly, and a pair of terminal members forsupplying electrical power to the heater, said method comprising thesteps of: inserting said terminal members into said openings in thehousing, portions of said terminals extending into said chamber;inserting said heater and said switch assembly into said chamber withthe heater in conductive electrical contact with said portions of theterminals and in heat-transfer relation with the switch assembly;installing a cover in said chamber to overlie the switch assembly andheater, said cover being engageable with said terminal members; andapplying a retainer across the mouth of the chamber to span the coverand engage the housing at the sides of the mouth of the chamber therebypositively securing the terminal members, the heater, the switchassembly and the cover in an assembled position relative to the housing.